Comparison of the reactions of some bisphosphines with two related dinuclear rhodium complexes

The reactions of some phosphines and bisphosphines with the dirhodium complexes (eta(5)-C5H5)(2)Rh-2(mu-CO)(mu(2)-eta(2)-CF3C2CF3) (I) and (eta(5):eta(5)-C5H4CH2C5H4)Rh-2(CO)(2)(mu(2)-eta(1):eta(1)-CF3C2CF3) (II) have been compared. The complexes (eta(5)-C5H5)(2)Rh-2(CO){eta(1)- Ph(2)P(CH2)(n)PPh(2)}(mu(2)-eta(1):eta(1)-CF3C2CF3) (III, n = 1-4), which are formed from (I) and the appropriate bisphosphine, all have a trans arrangement of the carbonyl and bisphosphine ligands, When left in solution, the complex (III, n=1) loses CO to form (eta(5)- C5H5)(2)Rh-2(mu(2)-eta(1):eta(1)-dppm)(mu(2)-eta(1):eta(1)-CF3C2CF3) (IV), but the other complexes are stable. The complex (II) was prepared to force a change of stereochemistry on the products of the addition reactions. Treatment of (II) with the phosphines P(p-MeC(6)H(4))(3) and PPh(2)H, and the bisphosphines Ph(2)P(CH2)(n)PPh(2) (n = 1-4) gave (eta(5):eta(5)-C5H4CH2C5H4)(2)Rh-2(CO)(L)(mu(2)-eta(1):eta(1)-CF3C2CF3) in which CO and L adopt a cis configuration on the Rh-Rh bond. UV irradiation of (eta(5):eta(5)-C5H4CH2C5H4)Rh-2(CO)(PPh(2)H)(mu(2)-eta(1):eta(1)-CF3C2CF3) (VII) results in formal insertion of the alkyne into the P-H bond to give (eta(5):eta(5)-C5H4CH2C5H4)Rh-2(CO)(mu(2)-PPh(2)C(CF3)C(CF3)H) (VIII). Unlike (III, n=1), (eta(5):eta(5)-C5H4CH2C5H4)Rh-2(CO)(eta(1)-dppm)(mu(2)-eta(1):eta(1)-CF3C2CF3) (IX, n=1) shows no tendency to lose CO in solution. Some bis(dinuclear) complexes [(eta(5)-C5H5)(2)Rh-2(CO)(mu(2)-eta(1):eta(1)-CF3C2CF3)](2)(mu-eta(1):eta(1)-Ph(2)P(CH2)(n)PPh(2))) (V, n = 2-4) and [(eta(5):eta(5)-C5H4CH2C5H4)Rh-2(CO)(mu(2)-eta(1):eta(1)-CF3C2CF3)](2)(mu-eta(1):eta(1)-dppb) (X) were formed when two equivalents of (I) or (II) were treated with the bisphosphine. The crystal and molecular structures of (III, n = 2), (IV) and (IX, n = 1) were determined by X-ray crystallography.